A projector is, for example, connected to a personal computer and used to make a presentation or any other performance. In this case, the projector is used to project the same image as that displayed on the personal computer on a screen or any other projection surface.
Such a projector is provided with a remote control unit that allows a user to change input video images and adjust a projected image. The remote control unit sends an infrared signal according to user's operation to the projector. A pointing stick for pointing an image projected and displayed by the projector is also frequently used in a presentation.
There have been known data input apparatus and image display apparatus to which data is inputted by using an input pen that emits infrared light or blue light (see JP-A-2006-243850 and JP-A-53-66122, for example).